The present invention concerns a system for compensating for color deviation in an image produced by an image capturing and reproducing apparatus such as a camera.
Conventionally an image capturing and reproducing apparatus such as a color charge coupled device (CCD) camera contains an auto white balance function to compensate for color deviation in an image taken. This function electrically balances the intensities of the green color component, red color component, and blue color component of the image signal so that the reproduced image will have a reproduced color similar to the original color of the object.
FIG. 1 for illustrates a conventional electronic auto white balance system, wherein a camera 11 is connected to an image processing circuit 12, which in turn is connected to color separation circuit 13 for separating the video signal from the image processing circuit 12 into a green, red and blue signal. Also included is a video a signal synthesizing and comparing circuit 14 for balancing the green, red and blue signal. In operation, the output signals of the camera 11 are applied to the image processing circuit 12, which generates a video signal to be separated by the color separation circuit 13 into green, red and blue signals. The green, red and blue signals from the synthesizing and comparing circuit 14 are then again applied to the image processing circuit 12. This conventional system makes the sum of all the color vectors white, in order to obtain a balanced image with respect to the whole screen. However, if the original image contains predominant proportions of certain colors compared to other colors, an unbalanced combination of color vectors is produced which reduces the gain of the predominant colors only, so that the predominant colors as reproduced, are considerably different from the original object colors.
Another conventional way to compensate for color deviation is to use color filters, as shown in FIG. 2. The colors of a picture taken by a silver halide camera 22 are considerably affected by weather. The color temperature appears at more than 7000K in the morning, giving bluish colors, or on a cloudy day appearing with a low temperature of about 5000K, giving reddish colors. In order to eliminate such drawbacks, a variety of color filters 21 are used when taking a picture with the silver halide camera. However, the filters are selected depending on the user's experience and the replacement of a filter is tedious work. Moreover, the number of available filters is too limited to satisfactorily compensate for all color deviations. In addition, a filter can not be mounted on a camera without a filter adapter such as a compact camera with a lens shutter.